The invention relates generally to tobacco curing and more particularly to a method of treating and curing tobacco leaves so as to have low levels of or no detectable tobacco-specific nitrosamines and a reduced level of bacterial endotoxins as compared to untreated, cured tobacco leaves, and to treatment of cured tobacco so as to have low levels of or no bacterial activity, fungal activity or bacteria on cured tobacco during or after storage.
It has been reported that air-cured and flue-cured tobacco contain tobacco-specific nitrosamines (TSNAs). See, xe2x80x9cEffect of Air-Curing on the Chemical Composition of Tobaccoxe2x80x9d, Anna Wiernik et al., Recent Adv. Tob. Sci, (1995), 21, pp. 39-80. According to Wiernik et al., TSNAs are not present in significant quantities in growing tobacco plants or fresh cut tobacco (green tobacco), but are formed during the curing process. Bacterial populations which reside on the tobacco leaves are stated to largely cause the formation of nitrites from nitrate during curing and possibly effect the direct catalysis of the nitrosation of secondary amines at physiological pH values. The affected secondary amines include tobacco alkaloids, which form TSNAs when nitrosated.
Various treatments of tobacco plants or harvested tobacco leaves have been suggested to reduce TSNA formation, including microwaving of flue-cured tobacco leaves (WO 98/58555).
Because curing of tobacco leaves is normally performed by the farmer who grows the tobacco, a simple, economical and non-labor-intensive method of reducing the bacterial population and/or activity, TSNA levels and bacterial endotoxin levels of the cured tobacco leaves is desirable.
The invention provides a treatment for tobacco leaves prior to or during curing which results in reduced or eliminated amounts of tobacco-specific nitrosamines, bacteria, bacterial activity and bacterial endotoxins in the cured tobacco leaves as compared to untreated cured leaves, and a treatment for cured tobacco leaves resulting in reduced or eliminated amounts of bacteria, bacterial activity, and/or fungal growth on stored cured tobacco leaves. The treatments include the use of effective amounts of one or more bactericidal gases, alone or in combination with one or more bactericidal treatments, such as wash solutions, visible or ultraviolet radiation, and sonic oscillation on the tobacco leaves.
In a first preferred embodiment, a tobacco leaf is treated with one or more bactericidal gases before or during curing, wherein upon completion of the curing process the treated tobacco leaf has a reduced or eliminated amount of tobacco-specific nitrosamines, bacterial endotoxins, bacteria, bacterial activity and/or fungal activity compared to non-treated cured tobacco.
In another embodiment, a tobacco leaf is treated with a combination of one or more bactericidal gases and at least one other bactericidal treatment before or during curing, wherein the other bactericidal treatment is selected from a wash solution, visible or ultraviolet light, sonic oscillation or a combination thereof, and wherein the treated tobacco leaf has one or more of a reduced or eliminated amount of tobacco-specific nitrosamines, bacteria, bacterial activity, fungal activity or bacterial endotoxins compared to non-treated cured tobacco.
In another embodiment, a cured tobacco leaf is treated with one or more bactericidal gases after curing and before and/or during storage, wherein upon completion of storage, the treated cured tobacco leaf has a reduced or eliminated amount of bacteria, bacterial activity and/or fungal activity as compared to non-treated stored cured tobacco.
In another embodiment, a cured tobacco leaf is treated with a combination of one or more bactericidal gases and at least one other bactericidal treatment after curing and before or during storage, wherein the other bactericidal treatment is selected from a wash solution, visible or ultraviolet light, sonic oscillation or a combination thereof, and wherein the treated cured tobacco leaf has one or more of a reduced or eliminated amount of bacteria, bacterial activity and/or fungal activity compared to non-treated stored cured tobacco.
In another embodiment, a method of reducing or eliminating tobacco-specific nitrosamines, bacterial populations, bacterial activity, fungal activity and/or bacterial endotoxins from uncured or cured tobacco leaf is presented. The method includes treating the uncured or cured tobacco leaf with an effective amount of one or more bactericidal gases, and optionally one or more of a wash solution, an effective amount of visible or ultraviolet light or an effective amount of sonic oscillation.